download Mail on iPhone

I have an iMac, iPad and iPhone 4S. I have my own domain name with 5 different e-mail addresses. I have set up mail on each item and have had no problem receiving or downloading e-mails until the last month. I am no longer receiving e-mails on my iPhone but am receiving them on my iMac and iPad. I have checked all the settings and they all look ok so was just wondering if anybody had any ideas